US3177419A - Electric control devices - Google Patents

Electric control devices Download PDF

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US3177419A
US3177419A US85835A US8583561A US3177419A US 3177419 A US3177419 A US 3177419A US 85835 A US85835 A US 85835A US 8583561 A US8583561 A US 8583561A US 3177419 A US3177419 A US 3177419A
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supply
excitation
motor
reactor
source
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Brooke Wilfrid
Howe Harry
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/005—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for remote controlled apparatus; for lines connecting such apparatus
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B11/00—Automatic controllers
    • G05B11/01—Automatic controllers electric
    • G05B11/012—Automatic controllers electric details of the transmission means
    • G05B11/016—Automatic controllers electric details of the transmission means using inductance means
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H11/00—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result
    • H02H11/005—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result in case of too low isolation resistance, too high load, short-circuit; earth fault
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/08—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for dynamo-electric motors
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/02—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using supply voltage with constant frequency and variable amplitude
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02B90/20—Smart grids as enabling technology in buildings sector
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S20/00—Management or operation of end-user stationary applications or the last stages of power distribution; Controlling, monitoring or operating thereof
    • Y04S20/14—Protecting elements, switches, relays or circuit breakers

Definitions

  • This invention relates to improvements in electric remote control devices of the saturable reactor type where the latter are employed for controlling single or polyphase electric power supplies to, for example, motors and other apparatus with which the devices are directly or indirectly connected in series, and more particularly where such devices are employed for establishing or disestablishing a supply to such circuits which are permanently closed without the necessity of making or breaking the main current, and using apparatus such as described in our application No. 23,815 now Patent No. 3,054,944, or their equivalent.
  • the object of the invention is to provide in apparatus of the kind referred to an effective form of push button remote control through which means forprotecting the circuit being controlled together with the apparatus operating therein are realised by providing one or more of the following:' (1) no volt protection, (2) inching, (3) overload protection, (4) short circuit prevention and protection, (5) phase failure protection, (6) safe means of isolation-within the normal interpretation of these terms.
  • a saturable reactor arrangement of the type described in our application referred to or of any similar or conventional type is connected in series with, for example, a squirrel cage motor to an AC. single or polyphase supply system and provided with the usual arrangements whereby supplementary excitation may be applied to the reactor or reactors in order to reduce the'impedance of same thus enabling sufficient current to pass to start the motor or conversely to increase the impedance of the reactors thereby reducing the current to a sufiiciently low value to stop the motor by interrupting the supplementary excitation supply and there are provided two supplementary excitation sources of rectified A.C.
  • the two excitation sources of rectified A.C. supply are assumed to be derived from a single phase supply system when the apparatus is being operated from such a supply system it is desirable that where the apparatus is operating on a polyphase supply system that the two rectified excitation supplies are also derived from polyphase sources.
  • the two excitation sources of supply are mutually interlocked by being connected in series or in parallel on the DC. side during starting so that when supplementary excitation is applied to the reactor system from the supply side source by closing a normally open start push button switch the impedance of the reactor or reactors which is normally high in the unexcited condition now becomes low, and the AC. voltage across same becomes transferred to the motor which starts up, whilst the load side excitation supply source now and for the time being becomes a supply source which automatically takes over the excitation of the reactor in place of the original supply source when the start push button is released, meantime the motor continues to run whilst the reactor is thus self-excited.
  • a normally closed stop button is provided in the excitation circuit which, when pressed, opens the latter and de-energises the reactor whereupon its impedance rapidly rises to its previously high unexcited value, and the AC. volts across the motor largely disappears and reappears across the reactor and the motor consequently stops, since the load side source of excitation is now no longer alive and the motor can only be re-started by pressing the start button through which the reactor is excited from the supply side source of supply, hence if there is a voltage failure the motor having stopped will not involuntarily restart when the supply is rein stated, thus providing no-voltage protection as it is normally understood.
  • the two rectified excitation supply sources are connested in parallel during starting the load side source takes over from the supply side source when the motor has accelerated to full speed, and the supply side source becomes disconnected on releasing the start button through which the excitation from the latter is applied. Unlike the series connected arrangement the two supplies do not boost each other.
  • the supply side excitation may be derived from a transformer the primary windings of which may be connected across the incoming supply lines or their equivalent or may alternatively be connected across the or each of the reactors or as a further alternative a suitable secondary winding may be provided on the or each reactor and connected directly to the supply side rectifier system thereby dispensing with the supply side transformer.
  • the supply and load side excitation may be still connected in series or parallel during starting but in the case of the two latter alternatives no boost feature during starting is available since the excitation supply voltage from these sources diminishes to zero as the motor runs up to speed.
  • Overload protection may be provided by the employment of conventional overload devices either of the thermal or electro-magnetic type which are arranged to open the excitation circuit only of the reactor when an overload occurs whilst the motor is running, the operation being equivalent to the pressing of the stop button, as already described, thus the motor stops due to the rapid increase in the impedance of the reactor and the arms-1s a consequent reduction in thecurrent to magnetising current value, and will not restart involuntarily in View of the no-volt protection features provided, although the main circuit stillremains unopened.
  • conventional overload devices either of the thermal or electro-magnetic type which are arranged to open the excitation circuit only of the reactor when an overload occurs whilst the motor is running, the operation being equivalent to the pressing of the stop button, as already described, thus the motor stops due to the rapid increase in the impedance of the reactor and the arms-1s a consequent reduction in thecurrent to magnetising current value, and will not restart involuntarily in View of the no-volt protection features provided, although the main circuit stillremains unopened.
  • circuit breakers usually break all the supply phases simultaneously on a polyphase system even on unbalanced faultsthat is to say where only one phase is faulted-no such mutual interlock is normally available between fuses if the latter are employed for overload protection, in that, if as is often the case only one fuse blows, the polyphase supply immediately becomes a Single phase one with its obvious dangers where polyphase motors are operating, thus the application of fuses for fault protection is somewhat limited in circuits wherein polyphase motors operate in the absence of some form of phase-failure protection which is not easy to arrange with conventional control apparatus.
  • One of the objects of the invention is to provide means for preventing heavy short-circuiting currents.
  • a short circuit may occur across only a part of the system, for example, across a pair of phases as distinct from a balanced short circuit across allphases.
  • phase failure protection is not effective when the motor is running light in that the latter will continue to run light on single phase, in which condition no danger exists, but a small load current of approximately half load valve will provide a sufficiently balanced condition in the load side excitation to shut down the motor and the protection ensures that the motor windings cannot become thermally overloaded which is its objective.
  • Phase failure is provided against lack of continuity of the circuit connections up to the point where the load side source of excitation supply is situated which would normally include the reactors and anything on the supply side thereof. If the whole circuit on the load side of the reactors is to be protected up to the terminals of the motor all that is necessary is to connect the primaries of the load side three-phase potential transformer direct to the motor terminals when the protection would be operative right up to the motor.
  • Phase failure protection is a feature of particular importance, as only where this is provided can fuses be safely employed in the three-phase motor control systems, since there is otherwise no means of providing an interlock ensuring that the blowing of one fuse would completely disestablish the supply in all three phases.
  • Safe means of isloation are provided by arranging an auxiliary blade on the isolating switch which breaks earlier and makes later than the main blades ensuring that the main circuit can only be broken or made when the impedance of the reactor system is of maximum valve that is to say when they are unexcited.
  • FIGURES 1 and 2 and 3 are circuit diagrams showing typical applications of the protection on inductive devices operating on a single-phase supply system.
  • FIGURES 4 and 5 show corresponding arrangements as applied to inductive devices operating on a three phase supply system
  • FIGURES 6, 7, 8 and 9 are schematic diagrams showing alternative arrangements for providing the supply side excitation for single and three phase systems.
  • a saturated reactor arrangement such as is described in our application No. 23,815 wherein a reactor C comprises cores A and B on which are provided the main windings PA PA2, P131 and PB nowadays connected between the terminals 4 and 5, and the excitation windings NA NR1, NAZ and NBZ between terminals 6-7 and 8-9 the reactor operating in series with a squirrel cage motor M from a single phase supply source Ll-N, that is to say, between phase and neutral of a three-phase supply system where the neutral is usually earthed or on an equivalent single phase supply.
  • An isolating switch V is shown having a main blade V1 in the main supply lead L1 and a blade V2 in the return lead N and an auxiliary blade V4 for breaking the control circuits of the reactor, ahead of the main blades.
  • a single-pole conventional type overload relay Z is shown, the operating coil of same being connected in the lead between the reactor and the motor.
  • Two potential transformers are shown at E and G, the former having its primary winding Ep connected across the live supply source between terminal 4 and the neutral lead Na through connections 16 and 1'7 which produces an output voltage from secondary windings Es, providing a rectified source of excitation supply through bridge rectifier F to which it is connected by connections 18 and 19-this will be referred to as the supply side source of excitation supply and is available always when the supply system is alive.
  • Transformer G is arranged with its primary winding Gp energised from the dead side or motor side of the reactor C between terminal 5 and the neutral lead Na through connections 12 and 13 respectively.
  • This provides an ancillary source of excitation supply through secondary winding Gs and bridge rectifier H connected thereto by connections 14 and 15.
  • the source of supply from the latter is available only when the motor M is 7 running and will be referred to as the load side source of excitation supply.
  • the two sources of supply are interlocked, in that they are connected in series during starting so that when excitation is applied to the reactor from the supply side source of supply a return is made through the load side rectifier system and that when the motor speeds up, the excitation of the reactor is taken over by the load side source of supply which has now become alive.
  • variable resistance R1 and Rd in the excitation supply circuits are provided for the purpose of varying the excitation supply voltage of the supply side and load side sources respectively, the former controlling the rate of acceleration during starting and thus enabling the starting current to be reduced or increased to required values whilst the latter resistance controls the impedance level at which the reactor works when the motor is running and consequently determines the voltage across the motor terminals when the latter is running under load.
  • Inching control is a usual requirement in connection with remote control systems Where small amounts of motion are required from the motor for adjustment and setting up purposes of the equipment which the motor is intended to drive so that the motor will respond to the pressing of a button for starting and stopping it as distinguished from the normal use of the start button which starts the motor but does not stop it.
  • the action of the arrangement is based on the excitation supply being provided from the supply side source and that the load side source is cut out by the change-over switch Y so that the interlocking feature or the follow up by the load side source of excitation as normally provided has been interrupted the excitation being provided from the positive terminal 35 of the rectifier F, through connection 4i auxiliary switch blade V4, connection 4:2, terminal 63 on the reactor C, through the excitation winding system to terminals 7-), through choke D, contacts 43 and 44 of the overload relay Z, connection :1, through variable resistance Rp which provides independent variation of the inching torque, through the change-over switch Y in the dotted position, through stop button I, through start button K, used as an incling button, through variable resistance R1 to negative terminal as of rectifier F, thus providing a safe method.
  • FIGURE 2 shows a variation of the arrangement of FIGURE 1, in that, the supply side and load side rectified sources of excitation supply are mutually interlocked during starting by parallel instead of series connection.
  • This arrangement differs from the former one one only, in that, due to the parallel connection of the two excitation supply sources the bypass rectifier U shown in FIGURE 1, is omitted, since it is no longer required, and that the switch Y1 for changing over from starting to inching now becomes a double-pole on-off switch, the operation of the arrangement being as follows:
  • the inching arrangement shown in FIGURE 2 is generally similar to that described in connection with FIGURE 1, in that, on opening the switch Y1 the upper pole of Amsterdamsconnects the load side source of excitation supply which otherwise provides the retaining excitation circuit and at the same time introduces the variable resistance Rp into the control circuit and the start button is then employed for inching purposes-the inching torque being determined by the variable resistance Rp precisely as in the FIGURE 1 arrangement.
  • FIGURE 3 shows a similar arrangement to that of FIGURE 1, except that two reactors C and Ca each wound for half of the line voltage are employed, the former connected in the L1 supply lead and the latter in the L2 supply lead with the motor M in series with them on the load side, thus providing a double-pole equipment suitable for use across one phase of a three-phase supply system which may or may not have an earthed neutral, or on an equivalent single-phase supply.
  • a double-pole overload relay Z is provided as shown.
  • FIG. 4 shows a corresponding application of the invention to three-phase supply systems and corresponds to the FIGURE 1 arrangement.
  • three reactors C, Ca and Cb of the type already described are employed connected one in each of the lines L1, L2 and L3 of a three-phase supply system and star connected with a squirrel cage motor M.
  • An isolating switch V is shown having main iblades V1, V2 and V3 in the main supply leads L1-L2 and L3 respectively and an auxiliary blade V4 for breaking the control circuits of the reactors in advance of the main blades.
  • a three pole conventional type overload relay Z is shown with an operating coil in each lead between the reactors and the motor.
  • Two three-phase potential transformers are shown at E and G, the primary Winding Ep of the former from terminals 29, 30 and 31 being connected to the supply terminals 4, 4a and 4b on the supply side of the reactors C, Ca and Cb respectively, whilst the primary windings Gp of the other transformer G are connected from terminals 25, 24 and 23 on same to terminals 5, 5a and 512 on the load side of the reactors.
  • the secondary windings Es of transformer E are connected to the three-phase supply side rectifier Fa from terminals 32-33 and 34 on same providing a supply side rectified excitation source of supply at the positive and negative terminals 35 and 3d respectively.
  • the secondary windings Gs of transformer G are likewise connected to a three-phase rectifier Ha from terminals 2627 and 28 on same, providing a load side rectified excitation source of supply at the positive and negative terminals 37 and 38 respectively.
  • a normally open start push button K and a normally closed stop push button I together with the variable resistances R1, Rd, Rp, change-over switch Y and bypass rectifier U are provided precisely as in FIGURE 1 arrangement-under like references.
  • the rectified excita tion source of supply flows from the positive terminal 35 of the supply side rectified Fa, through connection 4t) auxiliary switch blade V4, connection 42 to terminals 6-8 of the excitation winding system on reactor C, from terminals 7-9 on the latter through connections 47 and 48 to excitation winding terminals 6a and 8a respectively on reactor Ca, out from terminals 7a and 9a on the latter through connections 49 and 5d respectively to excitation winding terminals 6b-8b on reactor Cb, out from terminals lb-9b on the latter through contacts 43-44 on overload relay Z, connection 41, through change-over switch Y in the position as shown, through variable resistance Rd to negative terminals 33 on the three-phase load side rectifier Ha, through the rectifier elements of the latter-not yet providing any output voltage-to positive terminal 37, through stop button J, through start button-K now depressed, through variable resistance Rlback to the supply side rectifier Fa at negative terminal 36, thus exciting the three reactors collectively and simultaneously whereupon the impedance of same
  • the motor accelerates the load side transformer G-the primary windings of which are connected virtually in parallel with the motor-provides a secondary output voltage, the rectified equivalent of which appears across the terminals 37 and 38 of the three-phase load side rectifier Ha which now becomes additive to the rectified voltage existing across terminals 35 and 36 of the three-phase supply side rectifier Pa and boosting the latter and increasing the acceleration whilst the start button K remains depressed.
  • FIGURE 5 shows a variation of the latter arrangement differing only, in that, the supply side and load side rectified sources of excitation supply are connected in parailel during starting instead of in series, and corresponds with the FIGURE 2 arrangement, the operation being precisely as described in connection with the latter wherein the same notation of the control circuit details has been employed.
  • the overall operation is otherwise equivalent to the FIGURE 4 arrangement, except that the supply and load circuit excitation sources are not additive and consequently the :boost features previously mentioned are not produced. Unless heavy starting torques are particularly required there is no object in producing boost excitation which needlessly increases the starting current.
  • overload relays Z which may be either of the electromagnetic or of the thermal type. These are arranged to break the excitation circuit at present overload values at contacts 43-44 and are equivalent in such an event to pressing stop button I whereupon the motor will stop and can only be restarted by pressing the start button K.
  • FIGURES 1, 2 and 3 For isolating the reactor system from the singlephase supply and arranged with blades V1 and V2 in supply leads Ll-LZ or L1N together with an auxiliary blade V4 arranged to cut oif the excitation supply source in advance of the main blades when opening, thus ensuring that the impedance of the reactors is increased to maximum before the main blades break circuit and enme ns suing thatthecurren-t is reduced to magnetising current level before the circuit is broken.
  • the supply side excitation is derived from the supply side transformer E the primary windings system of which is connected across the incoming supply system and the secondary output is rectified by the supply side rectifier F or Fa.
  • FIGURES 6, 7, 8 and 9 Alternative arrangements for providing the supply side excitation supply are shown in FIGURES 6, 7, 8 and 9.
  • the arrangement shown differs from that in FIGURES l, 2 and 3, in that, the primary winding Ep of supply side transformer E is energised from terminals 4 and 5 which are across the main reactor windings. In the unexcited condition of the main reactor C practically the whole of the line voltage exists across these two .points.
  • FIGURE 7 a secondary winding is provided on the reactor C at terminals -11 which is connected directly to the supply side rectifier F and provides the same results as'the arrangement of FIGURE 6 thus enabling the transformer E to be dispensed with.
  • Secondary windings as described are shown in dotted outline on the reactors in FIGURES l, 2 and 3, at terminals 10-11 and lflaella.
  • FIGURE 8 shows the polyphase arrangement corresponding to the single phase arrangement shown in FIG- URE 6 in that the primary phase Ep of the polyphase transformer E are each connected across a separate reactor instead of across the supply lines.
  • FIGURE 9 shows a polyphase arrangement corresponding to that of FIGURE 7 in that, the supply source to the supply side rectifier F is derived from secondary windings 10-11 provided on reactor C, 10a-11a on reactor Ca and Nib-11! on reactor Cb, thus dispensing with the supply side transformer E. Secondary'windings as described are alsoshown in dotted outline on the reactors in FIGURES 1 and 4, at terminals marked with corresponding references in FIGURE 9.
  • An important feature of the invention lies in the prevention of heavy short circuiting currents and the protection-whilst such fault conditions exist-aiforded by the apparatus when the excitation arrangements are provided from the supply and load side sources respectively, as herein described. This operates. in the following In anner 1 Referring to FIGURES 1 and 2, if it be assumed that the motor has been started by pressing the button K in the manner already described and that a short circuit develops between the line 5 and the neutral lead N on the load side of the reactor C, this will result in the load side potential transformer G being short circuited, since the primary winding of same is connected across these same points and hence the load side rectified excitation source of supply will immediately collapse and with it the supplementary excitation to the windings of the reactor C across terminals 6-8 and 7-9 which is the sole source of excitation to the reactor whilst the motor runs.
  • the reactor will become fully excited from the supply side rectifier F, thereby reducing the impedance of same but not to an extent as would allow the passage of abnormal short circuit currents; such currents would be limited to approximately that of the normal starting current of the motor as determined by the amount of the applied excitation, this current limiting feature being due to the harmonic impedance of the reactor system and the saturating influence of the feed back excitation and the harmonic frequencies created in the wave-form of the current passing in the load circuit as a result of the short circuit condition.
  • the motor may be restarted by pressing the start button K in the normal manner as already explained.
  • FIGURES 4 and 5 which show diagrammatically the polyphase equivalent of the arrangements shown in FIGURES l, 2 and 3 the functioning of the apparatus would be precisely as described in connection in FIGURES 1, 2 and 3.
  • the motor M has been started by pressing the start button K and that a balanced short circuit develops across all the three lines 5, 5a and 512 between the reactors and the motor M
  • the three phase load side transformer G will become short 'circuited also and the load side rectified excitation source of supply to the reactors will accordingly collapse thereby increasing the impedance of the reactors and in turn reducing the current passing through them to magnetising current level and the supply volts will become transferred from the motor to the reactors and the motor will stop.
  • the start button K is pressed whilst the fault still prevails the reactors will become fully excited from the supply side rectifier Fa, thereby reducing the impedance to a limited extent whereby due to the harmonic impedance of the reactor system brought about by the short circuit condition as already explained, the current permitted to flow becomes limited to approximately that of the starting current of the motor as determined by the amount of the applied excitation.
  • the motor M is running light when the phase failure occurs it will continue to run on single phase but at a reduced voltage due to the partial transfer of voltage from it to the reactor until load is applied up to say half load at which point it will drop out of step and shut down as the effect of the loading increases the transfer of voltage due to the unbalancing of the circuit becoming more balanced, as explained.
  • the net result of the protective feature is that it prevents any thermal overloading of the motor windings which is its objective.
  • Phase failure protection is provided in the circuit on the supply side of the apparatus and up to the point where the primary windings of the load side three phase transformer G is connected to the reactors. If the protection is required right up to the motor it merely becomes necessary to connect the primary windings Gp of the transformer G to the motor terminals 20-21 and 22 as shown dotted in FIGURE 4.
  • a device as claimed in claim 1 wherein a variable resistance is provided in the supply side rectifier system through which the excitation current and hence the initial current to the load circuit may be varied by varying the value of the variable resistance, thus controlling the impedance level of the reactors during starting.
  • a device as claimed in claim 1 for providing overload protection wherein an overload relay is arranged to break the excitation circuit of the reactor or reactors in event of overload.
  • a remotecontrol device comprising a saturable reactor system having a supply side and a load side between which extends a main circuit for connection in series with a load circuit for establishing and disestablishing a supply of AC. power to the load circuit by varying the impedance of the main circuit under the control of supplementary excitation applied to excitation windings provided on the reactor system, said supplementary excitation being derived from two excitation sources, one source deriving supply from a rectifier system and transformer means connected to the supply side of the reactor system and the other source deriving a supply from arectifier system and transformer means connected to the load side of the reactor system, the said two sources of excitation supply being interlocked in series together with contacts of a starting push button switch so that the rectifier system of the load side source is employed as a continuity path for the supply side excitation during initial starting when the push button contacts are closed, there being provision of a rectifier for by-passing the contacts of the start push-button when the latter is released after starting thus maintaining the continuity in the excitation supply during
  • a device as claimed in claim wherein a variable resistance is provided through which the excitation current may be increased or decreased by means of which the inching current through the motor may be varied thus varying the torque provided for inching, the starting and stopping of the motor both being under control of the"start contact and the amount of motion provided by the motor being dependent upon the duration of time the start contact is made.
  • a remote control device for controlling an electric motor comprising a saturable reactor system having a supply side and a load side between which extends amain circuit for connection in series with the motor load for establishing and disestablishing a supply to the motor load by varying the impedance of the main circuit under the control of supplementary excitation applied to -ex-' citation windings provided on the reactor system, said supplementary excitation being derived from two excita-.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Power Engineering (AREA)
  • Motor And Converter Starters (AREA)
  • Control Of Ac Motors In General (AREA)
  • Testing Electric Properties And Detecting Electric Faults (AREA)
US85835A 1960-02-12 1961-01-30 Electric control devices Expired - Lifetime US3177419A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3387197A (en) * 1965-04-30 1968-06-04 Allen Bradley Co Primary speed control for an induction motor
US3763413A (en) * 1972-02-11 1973-10-02 J Wattenbarger Flux amplifier circuits for controlling induction motors and the like
CN106461737A (zh) * 2014-03-27 2017-02-22 阿尔斯通技术有限公司 变压器测试方法、电气测试系统、短路电路及阳极组件
CN113889966A (zh) * 2021-09-30 2022-01-04 大唐河北发电有限公司马头热电分公司 一种输煤皮带拉线及跑偏开关报警鉴别方法

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US2798170A (en) * 1954-07-07 1957-07-02 Clark Controller Co Magnetic amplifiers and control systems
US2958816A (en) * 1954-05-13 1960-11-01 Cutler Hammer Inc Saturable reactor motor control circuits

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US2958816A (en) * 1954-05-13 1960-11-01 Cutler Hammer Inc Saturable reactor motor control circuits
US2798170A (en) * 1954-07-07 1957-07-02 Clark Controller Co Magnetic amplifiers and control systems

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3387197A (en) * 1965-04-30 1968-06-04 Allen Bradley Co Primary speed control for an induction motor
US3763413A (en) * 1972-02-11 1973-10-02 J Wattenbarger Flux amplifier circuits for controlling induction motors and the like
CN106461737A (zh) * 2014-03-27 2017-02-22 阿尔斯通技术有限公司 变压器测试方法、电气测试系统、短路电路及阳极组件
CN106461737B (zh) * 2014-03-27 2020-06-16 通用电气技术有限公司 变压器测试方法、电气测试系统、短路电路及阳极组件
CN113889966A (zh) * 2021-09-30 2022-01-04 大唐河北发电有限公司马头热电分公司 一种输煤皮带拉线及跑偏开关报警鉴别方法

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NL261102A (oth) 1964-05-11
GB943203A (en) 1963-12-04

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